How to autofire.
1. Select a ring by clicking on it. You can do this while not in range of an animated. For example, Hack is highlighted.
2. If you see a target. Double click on that target with your mouse. Your avatar will then walk towards it to get in range so it can attack it.
As has been mentioned, what you're describing is 'Auto-move-in-range' - Auto-fire is not an option, so much as a click modifier. If you click an enemy while pressing the auto-fire key (Shift, by default) the game will automatically attempt to use whatever ring is presently selected. Specifically, by using auto-fire, you don't need to double-click - a single Shift-click will do precisely what you're describing. I'm not sure who finds Shift-click easier than double-click, but that's essentially what auto-fire allows. sweatdrop
Additionally, your first step can be eliminated through the Ring auto-selection option, through which the game will automatically select the first ring in one's tray that can affect a given target. Assuming Hack is the first ring in one's tray, one can double- or Shift-click an enemy while Bandage or a buff is currently highlighted, while auto-selection is active, and achieve the same effect you describe... 3nodding